I am wondering what is the best way to get to the hotel from the airport. Do all of the hotels have shuttle buses? Should we just plan to pick up a rental car at the airport?

Some hotels in Aruba don't have shuttle bus services. There's no need for you to worry because you've got many options. You can ride a taxi from the airport to the hotel. The rate per hour is $45. You can rent a car for convenient travel. There are many bus-stops outside the airport so you can even ride a bus. It's really all up to you.

I am just curious. If we should decide to take a bus to our hotel instead of rent a car, how would we know which bus to take?

It depends, what hotel are you planning to stay at? Many of them do have shuttles/transfers, but some do not. The one we used cost about $20 I believe.

We are considering staying at the Tamarijn hotel, but aren't 100 percent sure yet. How would we get to the hotel, how long would it take and how much would it cost?

Belisarius,

Was that $20 a piece or was that for your entire family? How many were you? If that is per individual, I find that quite expensive. We are used to travelling by bus in Chile, South America where it costs approximately 75 cents per person to go the entire bus route.